SparkFun Forums

[deflater]

I am working on some daisy-chainable shift register boards, and I can get most of it done on one layer except for the Vcc/GND busses. I was thinking of buying some double sided copper clad board and making a couple of wider tracks on the reverse side that I could just drill through to get to Vcc without worrying too much about alignment.

Has anyone done something similar? My only worry is that drilling without any holes etched on the reverse side will push the copper off.

[Philba]

I've made lots of dual layer boards and never had a problem with that. biggest problems I've seen are having poor alignment of the two sides and lack of plated through holes. Make sure you use sharp drill bits.

[deflater]

Ah, but the point was that I didn't intend to align the sides much at all. I just plan to put a wide track on the other side of the emitters of my 32 BJTs and just drill where the pins happen to fall.

When I can get to the local component store I'll have to buy some boards and try it out.

[no first name supplied]

I don't think you'll have a problem with the copper coming off, it's stuck pretty well.

[bigglez]

Greetings (No First Name Supplied),

My only worry is that drilling without any holes etched on the reverse side will push the copper off.

That is a concern if you try drilling without a backing board.
Most PCB shops stack boards for drilling, and add a scrap
piece of FR-4 on the bottom to stop the last board from
breaking out.

Your proposed technique (blind drilling into the bottom
layer to make a bus) will work well.

Comments Welcome!

[no first name supplied]

I think you're replying to the wrong guy

[MarkS]

I think you're replying to the wrong guy

Nope. He does that to anyone that posts a question and doesn't give their name. Your user name is just a coincidence.

[macegr]

I think you're replying to the wrong guy

Nope. He does that to anyone that posts a question and doesn't give their name. Your user name is just a coincidence.

I highly doubt that user name is a coincidence. Quite funny though.

[deflater]

The backing board is a good idea. I've got plenty of incorrect boards sitting around taunting me that I can have my revenge on.

[Philba]

be careful using boards that have been previously drilled for backing. It is possible to cause the drill bit to flex and break if you hit the edge of a hole in the backer.

I've used pressboard (sort of thin MDF) for backing. It works OK. The best backing is aluminum clad pressboard. It's what PCB houses use. I got a ton of the stuff at an auction for a PCB house that went out of business.

[winston]

I've had great results doing my own double sided boards (I've not had a failure due to misalignment yet, after doing about a dozen of them!) - for things that really do need decent registration.

It's not difficult if you're careful getting your toner transfer (or other etch resist method, if you prefer photo resist) sheets lined up correctly. I've not had a problem when drilling, even for fairly small vias.

One thing you need to remember is you've got to be a bit more careful about via placement - for vias made up of component pins, you need to make sure the component is one you can get the soldering iron to both sides, and when placing vias, often a via underneath a SMD is out of the question, because the bit of wire or track pin making up the via will probably stand too tall to live underneath many SMD packages. But from how you've described the project that doesn't sound like it'll be an issue in this instance.

[gussy]

I think you're replying to the wrong guy

No, Peter used capitals, your name has no capitals. Different person.

Nice try though.